March 22 (Reuters) - Wall Street was mixed on Wednesday as investors focused on President Donald Trump's struggle to push through a healthcare bill and worried that promised tax cuts may face similar hurdles.

U.S. stocks in the previous session had their worst day since before Trump's election as investors worried that the president's struggle to overhaul healthcare was a sign he would also face trouble pushing through promised corporate tax cuts that have been behind the market's record-breaking rally since November.

Trump and Republican lawmakers appeared to be losing the support they need for controversial healthcare legislation scheduled for a vote in the House of Representatives on Thursday. Losing or delaying the vote would bruise investors' confidence in Trump's legislative ability and his ability to keep his big promises to business.

"If that happens, you could see a little bit of volatility in the market," said David Schiegoleit, managing director at U.S. Bank Private Client Reserve in Los Angeles.

Apple rose 1.2 percent and provided the biggest boost to the three major indexes.

The Dow was lower, weighed down by a 7-percent fall in Nike after the world's largest footwear maker missed quarterly revenue estimates.